1 /* handling of writes to regular files and writing back to the server 2 * 3 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public License 8 * as published by the Free Software Foundation; either version 9 * 2 of the License, or (at your option) any later version. 10 */ 11 #include <linux/backing-dev.h> 12 #include <linux/slab.h> 13 #include <linux/fs.h> 14 #include <linux/pagemap.h> 15 #include <linux/writeback.h> 16 #include <linux/pagevec.h> 17 #include "internal.h" 18 19 static int afs_write_back_from_locked_page(struct afs_writeback *wb, 20 struct page *page); 21 22 /* 23 * mark a page as having been made dirty and thus needing writeback 24 */ 25 int afs_set_page_dirty(struct page *page) 26 { 27 _enter(""); 28 return __set_page_dirty_nobuffers(page); 29 } 30 31 /* 32 * unlink a writeback record because its usage has reached zero 33 * - must be called with the wb->vnode->writeback_lock held 34 */ 35 static void afs_unlink_writeback(struct afs_writeback *wb) 36 { 37 struct afs_writeback *front; 38 struct afs_vnode *vnode = wb->vnode; 39 40 list_del_init(&wb->link); 41 if (!list_empty(&vnode->writebacks)) { 42 /* if an fsync rises to the front of the queue then wake it 43 * up */ 44 front = list_entry(vnode->writebacks.next, 45 struct afs_writeback, link); 46 if (front->state == AFS_WBACK_SYNCING) { 47 _debug("wake up sync"); 48 front->state = AFS_WBACK_COMPLETE; 49 wake_up(&front->waitq); 50 } 51 } 52 } 53 54 /* 55 * free a writeback record 56 */ 57 static void afs_free_writeback(struct afs_writeback *wb) 58 { 59 _enter(""); 60 key_put(wb->key); 61 kfree(wb); 62 } 63 64 /* 65 * dispose of a reference to a writeback record 66 */ 67 void afs_put_writeback(struct afs_writeback *wb) 68 { 69 struct afs_vnode *vnode = wb->vnode; 70 71 _enter("{%d}", wb->usage); 72 73 spin_lock(&vnode->writeback_lock); 74 if (--wb->usage == 0) 75 afs_unlink_writeback(wb); 76 else 77 wb = NULL; 78 spin_unlock(&vnode->writeback_lock); 79 if (wb) 80 afs_free_writeback(wb); 81 } 82 83 /* 84 * partly or wholly fill a page that's under preparation for writing 85 */ 86 static int afs_fill_page(struct afs_vnode *vnode, struct key *key, 87 loff_t pos, unsigned int len, struct page *page) 88 { 89 struct afs_read *req; 90 int ret; 91 92 _enter(",,%llu", (unsigned long long)pos); 93 94 req = kzalloc(sizeof(struct afs_read) + sizeof(struct page *), 95 GFP_KERNEL); 96 if (!req) 97 return -ENOMEM; 98 99 atomic_set(&req->usage, 1); 100 req->pos = pos; 101 req->len = len; 102 req->nr_pages = 1; 103 req->pages[0] = page; 104 get_page(page); 105 106 ret = afs_vnode_fetch_data(vnode, key, req); 107 afs_put_read(req); 108 if (ret < 0) { 109 if (ret == -ENOENT) { 110 _debug("got NOENT from server" 111 " - marking file deleted and stale"); 112 set_bit(AFS_VNODE_DELETED, &vnode->flags); 113 ret = -ESTALE; 114 } 115 } 116 117 _leave(" = %d", ret); 118 return ret; 119 } 120 121 /* 122 * prepare to perform part of a write to a page 123 */ 124 int afs_write_begin(struct file *file, struct address_space *mapping, 125 loff_t pos, unsigned len, unsigned flags, 126 struct page **pagep, void **fsdata) 127 { 128 struct afs_writeback *candidate, *wb; 129 struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); 130 struct page *page; 131 struct key *key = file->private_data; 132 unsigned from = pos & (PAGE_SIZE - 1); 133 unsigned to = from + len; 134 pgoff_t index = pos >> PAGE_SHIFT; 135 int ret; 136 137 _enter("{%x:%u},{%lx},%u,%u", 138 vnode->fid.vid, vnode->fid.vnode, index, from, to); 139 140 candidate = kzalloc(sizeof(*candidate), GFP_KERNEL); 141 if (!candidate) 142 return -ENOMEM; 143 candidate->vnode = vnode; 144 candidate->first = candidate->last = index; 145 candidate->offset_first = from; 146 candidate->to_last = to; 147 INIT_LIST_HEAD(&candidate->link); 148 candidate->usage = 1; 149 candidate->state = AFS_WBACK_PENDING; 150 init_waitqueue_head(&candidate->waitq); 151 152 page = grab_cache_page_write_begin(mapping, index, flags); 153 if (!page) { 154 kfree(candidate); 155 return -ENOMEM; 156 } 157 158 if (!PageUptodate(page) && len != PAGE_SIZE) { 159 ret = afs_fill_page(vnode, key, pos & PAGE_MASK, PAGE_SIZE, page); 160 if (ret < 0) { 161 unlock_page(page); 162 put_page(page); 163 kfree(candidate); 164 _leave(" = %d [prep]", ret); 165 return ret; 166 } 167 SetPageUptodate(page); 168 } 169 170 /* page won't leak in error case: it eventually gets cleaned off LRU */ 171 *pagep = page; 172 173 try_again: 174 spin_lock(&vnode->writeback_lock); 175 176 /* see if this page is already pending a writeback under a suitable key 177 * - if so we can just join onto that one */ 178 wb = (struct afs_writeback *) page_private(page); 179 if (wb) { 180 if (wb->key == key && wb->state == AFS_WBACK_PENDING) 181 goto subsume_in_current_wb; 182 goto flush_conflicting_wb; 183 } 184 185 if (index > 0) { 186 /* see if we can find an already pending writeback that we can 187 * append this page to */ 188 list_for_each_entry(wb, &vnode->writebacks, link) { 189 if (wb->last == index - 1 && wb->key == key && 190 wb->state == AFS_WBACK_PENDING) 191 goto append_to_previous_wb; 192 } 193 } 194 195 list_add_tail(&candidate->link, &vnode->writebacks); 196 candidate->key = key_get(key); 197 spin_unlock(&vnode->writeback_lock); 198 SetPagePrivate(page); 199 set_page_private(page, (unsigned long) candidate); 200 _leave(" = 0 [new]"); 201 return 0; 202 203 subsume_in_current_wb: 204 _debug("subsume"); 205 ASSERTRANGE(wb->first, <=, index, <=, wb->last); 206 if (index == wb->first && from < wb->offset_first) 207 wb->offset_first = from; 208 if (index == wb->last && to > wb->to_last) 209 wb->to_last = to; 210 spin_unlock(&vnode->writeback_lock); 211 kfree(candidate); 212 _leave(" = 0 [sub]"); 213 return 0; 214 215 append_to_previous_wb: 216 _debug("append into %lx-%lx", wb->first, wb->last); 217 wb->usage++; 218 wb->last++; 219 wb->to_last = to; 220 spin_unlock(&vnode->writeback_lock); 221 SetPagePrivate(page); 222 set_page_private(page, (unsigned long) wb); 223 kfree(candidate); 224 _leave(" = 0 [app]"); 225 return 0; 226 227 /* the page is currently bound to another context, so if it's dirty we 228 * need to flush it before we can use the new context */ 229 flush_conflicting_wb: 230 _debug("flush conflict"); 231 if (wb->state == AFS_WBACK_PENDING) 232 wb->state = AFS_WBACK_CONFLICTING; 233 spin_unlock(&vnode->writeback_lock); 234 if (PageDirty(page)) { 235 ret = afs_write_back_from_locked_page(wb, page); 236 if (ret < 0) { 237 afs_put_writeback(candidate); 238 _leave(" = %d", ret); 239 return ret; 240 } 241 } 242 243 /* the page holds a ref on the writeback record */ 244 afs_put_writeback(wb); 245 set_page_private(page, 0); 246 ClearPagePrivate(page); 247 goto try_again; 248 } 249 250 /* 251 * finalise part of a write to a page 252 */ 253 int afs_write_end(struct file *file, struct address_space *mapping, 254 loff_t pos, unsigned len, unsigned copied, 255 struct page *page, void *fsdata) 256 { 257 struct afs_vnode *vnode = AFS_FS_I(file_inode(file)); 258 struct key *key = file->private_data; 259 loff_t i_size, maybe_i_size; 260 int ret; 261 262 _enter("{%x:%u},{%lx}", 263 vnode->fid.vid, vnode->fid.vnode, page->index); 264 265 maybe_i_size = pos + copied; 266 267 i_size = i_size_read(&vnode->vfs_inode); 268 if (maybe_i_size > i_size) { 269 spin_lock(&vnode->writeback_lock); 270 i_size = i_size_read(&vnode->vfs_inode); 271 if (maybe_i_size > i_size) 272 i_size_write(&vnode->vfs_inode, maybe_i_size); 273 spin_unlock(&vnode->writeback_lock); 274 } 275 276 if (!PageUptodate(page)) { 277 if (copied < len) { 278 /* Try and load any missing data from the server. The 279 * unmarshalling routine will take care of clearing any 280 * bits that are beyond the EOF. 281 */ 282 ret = afs_fill_page(vnode, key, pos + copied, 283 len - copied, page); 284 if (ret < 0) 285 return ret; 286 } 287 SetPageUptodate(page); 288 } 289 290 set_page_dirty(page); 291 if (PageDirty(page)) 292 _debug("dirtied"); 293 unlock_page(page); 294 put_page(page); 295 296 return copied; 297 } 298 299 /* 300 * kill all the pages in the given range 301 */ 302 static void afs_kill_pages(struct afs_vnode *vnode, bool error, 303 pgoff_t first, pgoff_t last) 304 { 305 struct pagevec pv; 306 unsigned count, loop; 307 308 _enter("{%x:%u},%lx-%lx", 309 vnode->fid.vid, vnode->fid.vnode, first, last); 310 311 pagevec_init(&pv, 0); 312 313 do { 314 _debug("kill %lx-%lx", first, last); 315 316 count = last - first + 1; 317 if (count > PAGEVEC_SIZE) 318 count = PAGEVEC_SIZE; 319 pv.nr = find_get_pages_contig(vnode->vfs_inode.i_mapping, 320 first, count, pv.pages); 321 ASSERTCMP(pv.nr, ==, count); 322 323 for (loop = 0; loop < count; loop++) { 324 ClearPageUptodate(pv.pages[loop]); 325 if (error) 326 SetPageError(pv.pages[loop]); 327 end_page_writeback(pv.pages[loop]); 328 } 329 330 __pagevec_release(&pv); 331 } while (first < last); 332 333 _leave(""); 334 } 335 336 /* 337 * synchronously write back the locked page and any subsequent non-locked dirty 338 * pages also covered by the same writeback record 339 */ 340 static int afs_write_back_from_locked_page(struct afs_writeback *wb, 341 struct page *primary_page) 342 { 343 struct page *pages[8], *page; 344 unsigned long count; 345 unsigned n, offset, to; 346 pgoff_t start, first, last; 347 int loop, ret; 348 349 _enter(",%lx", primary_page->index); 350 351 count = 1; 352 if (!clear_page_dirty_for_io(primary_page)) 353 BUG(); 354 if (test_set_page_writeback(primary_page)) 355 BUG(); 356 357 /* find all consecutive lockable dirty pages, stopping when we find a 358 * page that is not immediately lockable, is not dirty or is missing, 359 * or we reach the end of the range */ 360 start = primary_page->index; 361 if (start >= wb->last) 362 goto no_more; 363 start++; 364 do { 365 _debug("more %lx [%lx]", start, count); 366 n = wb->last - start + 1; 367 if (n > ARRAY_SIZE(pages)) 368 n = ARRAY_SIZE(pages); 369 n = find_get_pages_contig(wb->vnode->vfs_inode.i_mapping, 370 start, n, pages); 371 _debug("fgpc %u", n); 372 if (n == 0) 373 goto no_more; 374 if (pages[0]->index != start) { 375 do { 376 put_page(pages[--n]); 377 } while (n > 0); 378 goto no_more; 379 } 380 381 for (loop = 0; loop < n; loop++) { 382 page = pages[loop]; 383 if (page->index > wb->last) 384 break; 385 if (!trylock_page(page)) 386 break; 387 if (!PageDirty(page) || 388 page_private(page) != (unsigned long) wb) { 389 unlock_page(page); 390 break; 391 } 392 if (!clear_page_dirty_for_io(page)) 393 BUG(); 394 if (test_set_page_writeback(page)) 395 BUG(); 396 unlock_page(page); 397 put_page(page); 398 } 399 count += loop; 400 if (loop < n) { 401 for (; loop < n; loop++) 402 put_page(pages[loop]); 403 goto no_more; 404 } 405 406 start += loop; 407 } while (start <= wb->last && count < 65536); 408 409 no_more: 410 /* we now have a contiguous set of dirty pages, each with writeback set 411 * and the dirty mark cleared; the first page is locked and must remain 412 * so, all the rest are unlocked */ 413 first = primary_page->index; 414 last = first + count - 1; 415 416 offset = (first == wb->first) ? wb->offset_first : 0; 417 to = (last == wb->last) ? wb->to_last : PAGE_SIZE; 418 419 _debug("write back %lx[%u..] to %lx[..%u]", first, offset, last, to); 420 421 ret = afs_vnode_store_data(wb, first, last, offset, to); 422 if (ret < 0) { 423 switch (ret) { 424 case -EDQUOT: 425 case -ENOSPC: 426 mapping_set_error(wb->vnode->vfs_inode.i_mapping, -ENOSPC); 427 break; 428 case -EROFS: 429 case -EIO: 430 case -EREMOTEIO: 431 case -EFBIG: 432 case -ENOENT: 433 case -ENOMEDIUM: 434 case -ENXIO: 435 afs_kill_pages(wb->vnode, true, first, last); 436 mapping_set_error(wb->vnode->vfs_inode.i_mapping, -EIO); 437 break; 438 case -EACCES: 439 case -EPERM: 440 case -ENOKEY: 441 case -EKEYEXPIRED: 442 case -EKEYREJECTED: 443 case -EKEYREVOKED: 444 afs_kill_pages(wb->vnode, false, first, last); 445 break; 446 default: 447 break; 448 } 449 } else { 450 ret = count; 451 } 452 453 _leave(" = %d", ret); 454 return ret; 455 } 456 457 /* 458 * write a page back to the server 459 * - the caller locked the page for us 460 */ 461 int afs_writepage(struct page *page, struct writeback_control *wbc) 462 { 463 struct afs_writeback *wb; 464 int ret; 465 466 _enter("{%lx},", page->index); 467 468 wb = (struct afs_writeback *) page_private(page); 469 ASSERT(wb != NULL); 470 471 ret = afs_write_back_from_locked_page(wb, page); 472 unlock_page(page); 473 if (ret < 0) { 474 _leave(" = %d", ret); 475 return 0; 476 } 477 478 wbc->nr_to_write -= ret; 479 480 _leave(" = 0"); 481 return 0; 482 } 483 484 /* 485 * write a region of pages back to the server 486 */ 487 static int afs_writepages_region(struct address_space *mapping, 488 struct writeback_control *wbc, 489 pgoff_t index, pgoff_t end, pgoff_t *_next) 490 { 491 struct afs_writeback *wb; 492 struct page *page; 493 int ret, n; 494 495 _enter(",,%lx,%lx,", index, end); 496 497 do { 498 n = find_get_pages_tag(mapping, &index, PAGECACHE_TAG_DIRTY, 499 1, &page); 500 if (!n) 501 break; 502 503 _debug("wback %lx", page->index); 504 505 if (page->index > end) { 506 *_next = index; 507 put_page(page); 508 _leave(" = 0 [%lx]", *_next); 509 return 0; 510 } 511 512 /* at this point we hold neither mapping->tree_lock nor lock on 513 * the page itself: the page may be truncated or invalidated 514 * (changing page->mapping to NULL), or even swizzled back from 515 * swapper_space to tmpfs file mapping 516 */ 517 lock_page(page); 518 519 if (page->mapping != mapping) { 520 unlock_page(page); 521 put_page(page); 522 continue; 523 } 524 525 if (wbc->sync_mode != WB_SYNC_NONE) 526 wait_on_page_writeback(page); 527 528 if (PageWriteback(page) || !PageDirty(page)) { 529 unlock_page(page); 530 put_page(page); 531 continue; 532 } 533 534 wb = (struct afs_writeback *) page_private(page); 535 ASSERT(wb != NULL); 536 537 spin_lock(&wb->vnode->writeback_lock); 538 wb->state = AFS_WBACK_WRITING; 539 spin_unlock(&wb->vnode->writeback_lock); 540 541 ret = afs_write_back_from_locked_page(wb, page); 542 unlock_page(page); 543 put_page(page); 544 if (ret < 0) { 545 _leave(" = %d", ret); 546 return ret; 547 } 548 549 wbc->nr_to_write -= ret; 550 551 cond_resched(); 552 } while (index < end && wbc->nr_to_write > 0); 553 554 *_next = index; 555 _leave(" = 0 [%lx]", *_next); 556 return 0; 557 } 558 559 /* 560 * write some of the pending data back to the server 561 */ 562 int afs_writepages(struct address_space *mapping, 563 struct writeback_control *wbc) 564 { 565 pgoff_t start, end, next; 566 int ret; 567 568 _enter(""); 569 570 if (wbc->range_cyclic) { 571 start = mapping->writeback_index; 572 end = -1; 573 ret = afs_writepages_region(mapping, wbc, start, end, &next); 574 if (start > 0 && wbc->nr_to_write > 0 && ret == 0) 575 ret = afs_writepages_region(mapping, wbc, 0, start, 576 &next); 577 mapping->writeback_index = next; 578 } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) { 579 end = (pgoff_t)(LLONG_MAX >> PAGE_SHIFT); 580 ret = afs_writepages_region(mapping, wbc, 0, end, &next); 581 if (wbc->nr_to_write > 0) 582 mapping->writeback_index = next; 583 } else { 584 start = wbc->range_start >> PAGE_SHIFT; 585 end = wbc->range_end >> PAGE_SHIFT; 586 ret = afs_writepages_region(mapping, wbc, start, end, &next); 587 } 588 589 _leave(" = %d", ret); 590 return ret; 591 } 592 593 /* 594 * completion of write to server 595 */ 596 void afs_pages_written_back(struct afs_vnode *vnode, struct afs_call *call) 597 { 598 struct afs_writeback *wb = call->wb; 599 struct pagevec pv; 600 unsigned count, loop; 601 pgoff_t first = call->first, last = call->last; 602 bool free_wb; 603 604 _enter("{%x:%u},{%lx-%lx}", 605 vnode->fid.vid, vnode->fid.vnode, first, last); 606 607 ASSERT(wb != NULL); 608 609 pagevec_init(&pv, 0); 610 611 do { 612 _debug("done %lx-%lx", first, last); 613 614 count = last - first + 1; 615 if (count > PAGEVEC_SIZE) 616 count = PAGEVEC_SIZE; 617 pv.nr = find_get_pages_contig(call->mapping, first, count, 618 pv.pages); 619 ASSERTCMP(pv.nr, ==, count); 620 621 spin_lock(&vnode->writeback_lock); 622 for (loop = 0; loop < count; loop++) { 623 struct page *page = pv.pages[loop]; 624 end_page_writeback(page); 625 if (page_private(page) == (unsigned long) wb) { 626 set_page_private(page, 0); 627 ClearPagePrivate(page); 628 wb->usage--; 629 } 630 } 631 free_wb = false; 632 if (wb->usage == 0) { 633 afs_unlink_writeback(wb); 634 free_wb = true; 635 } 636 spin_unlock(&vnode->writeback_lock); 637 first += count; 638 if (free_wb) { 639 afs_free_writeback(wb); 640 wb = NULL; 641 } 642 643 __pagevec_release(&pv); 644 } while (first <= last); 645 646 _leave(""); 647 } 648 649 /* 650 * write to an AFS file 651 */ 652 ssize_t afs_file_write(struct kiocb *iocb, struct iov_iter *from) 653 { 654 struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp)); 655 ssize_t result; 656 size_t count = iov_iter_count(from); 657 658 _enter("{%x.%u},{%zu},", 659 vnode->fid.vid, vnode->fid.vnode, count); 660 661 if (IS_SWAPFILE(&vnode->vfs_inode)) { 662 printk(KERN_INFO 663 "AFS: Attempt to write to active swap file!\n"); 664 return -EBUSY; 665 } 666 667 if (!count) 668 return 0; 669 670 result = generic_file_write_iter(iocb, from); 671 672 _leave(" = %zd", result); 673 return result; 674 } 675 676 /* 677 * flush the vnode to the fileserver 678 */ 679 int afs_writeback_all(struct afs_vnode *vnode) 680 { 681 struct address_space *mapping = vnode->vfs_inode.i_mapping; 682 struct writeback_control wbc = { 683 .sync_mode = WB_SYNC_ALL, 684 .nr_to_write = LONG_MAX, 685 .range_cyclic = 1, 686 }; 687 int ret; 688 689 _enter(""); 690 691 ret = mapping->a_ops->writepages(mapping, &wbc); 692 __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); 693 694 _leave(" = %d", ret); 695 return ret; 696 } 697 698 /* 699 * flush any dirty pages for this process, and check for write errors. 700 * - the return status from this call provides a reliable indication of 701 * whether any write errors occurred for this process. 702 */ 703 int afs_fsync(struct file *file, loff_t start, loff_t end, int datasync) 704 { 705 struct inode *inode = file_inode(file); 706 struct afs_writeback *wb, *xwb; 707 struct afs_vnode *vnode = AFS_FS_I(inode); 708 int ret; 709 710 _enter("{%x:%u},{n=%pD},%d", 711 vnode->fid.vid, vnode->fid.vnode, file, 712 datasync); 713 714 ret = filemap_write_and_wait_range(inode->i_mapping, start, end); 715 if (ret) 716 return ret; 717 inode_lock(inode); 718 719 /* use a writeback record as a marker in the queue - when this reaches 720 * the front of the queue, all the outstanding writes are either 721 * completed or rejected */ 722 wb = kzalloc(sizeof(*wb), GFP_KERNEL); 723 if (!wb) { 724 ret = -ENOMEM; 725 goto out; 726 } 727 wb->vnode = vnode; 728 wb->first = 0; 729 wb->last = -1; 730 wb->offset_first = 0; 731 wb->to_last = PAGE_SIZE; 732 wb->usage = 1; 733 wb->state = AFS_WBACK_SYNCING; 734 init_waitqueue_head(&wb->waitq); 735 736 spin_lock(&vnode->writeback_lock); 737 list_for_each_entry(xwb, &vnode->writebacks, link) { 738 if (xwb->state == AFS_WBACK_PENDING) 739 xwb->state = AFS_WBACK_CONFLICTING; 740 } 741 list_add_tail(&wb->link, &vnode->writebacks); 742 spin_unlock(&vnode->writeback_lock); 743 744 /* push all the outstanding writebacks to the server */ 745 ret = afs_writeback_all(vnode); 746 if (ret < 0) { 747 afs_put_writeback(wb); 748 _leave(" = %d [wb]", ret); 749 goto out; 750 } 751 752 /* wait for the preceding writes to actually complete */ 753 ret = wait_event_interruptible(wb->waitq, 754 wb->state == AFS_WBACK_COMPLETE || 755 vnode->writebacks.next == &wb->link); 756 afs_put_writeback(wb); 757 _leave(" = %d", ret); 758 out: 759 inode_unlock(inode); 760 return ret; 761 } 762 763 /* 764 * Flush out all outstanding writes on a file opened for writing when it is 765 * closed. 766 */ 767 int afs_flush(struct file *file, fl_owner_t id) 768 { 769 _enter(""); 770 771 if ((file->f_mode & FMODE_WRITE) == 0) 772 return 0; 773 774 return vfs_fsync(file, 0); 775 } 776 777 /* 778 * notification that a previously read-only page is about to become writable 779 * - if it returns an error, the caller will deliver a bus error signal 780 */ 781 int afs_page_mkwrite(struct vm_area_struct *vma, struct page *page) 782 { 783 struct afs_vnode *vnode = AFS_FS_I(vma->vm_file->f_mapping->host); 784 785 _enter("{{%x:%u}},{%lx}", 786 vnode->fid.vid, vnode->fid.vnode, page->index); 787 788 /* wait for the page to be written to the cache before we allow it to 789 * be modified */ 790 #ifdef CONFIG_AFS_FSCACHE 791 fscache_wait_on_page_write(vnode->cache, page); 792 #endif 793 794 _leave(" = 0"); 795 return 0; 796 } 797